Usually, the reactive force of the wheel in rotation, is indicated of ωr=μr⋅G(kg) and the coefficient of resistance is μr=s/r=sin θ.
Affecting point of the vertical reactive force in soil, is upon the wheel, crossed of parrallel line at 1/3S from the vertical line, that drawn from the center of the wheel to earth.
But actually, the vector of reactive force of soil, is pass the center of the wheel always, therefore, we must be concerned about the affecting point of the compound vector, that is vertical and horizontal reactive force of soil resistance.
Affecting point of the vector of horizontal reactive force of soil is upon the wheel, crossed of parallel line at 1/3d under from the earth line.
Therefore, at the case of d=r, the affecting point is become the center point of arc A-B, and even if, at the out of case, the point is near the center of the arc, attaching to the soil.
From this result, we know the formula of reaction of the wheel in rotation is indicated of next formula.
ωr=G⋅sinθ/2(kg) μr=sin θ/2